Apparatus for heating air



Jan. 23, 1962 R. G. HICKS APPARATUS FOR HEATING AIR Filed April 21, 1958 INVENTOR. ROBERT G. HICKS FIG. 2

ATTORNEY 3,17,877 APPARATUS FOR HEATING Am Robert G. Hicks, llettendorf, Iowa, assignor to American Air Filter Company, Inc, Louisville, Ky, a corporation of Delaware Filed Apr. 21, 1 958, Ser. No. 729,784 4 Claims. (Cl. 126-llltl) This invention relates to an apparatus for heating a gaseous medium and more particularly to a method and apparatus for heating air in a controlled manner to obtain efiicient air heating results over a wide range of ambient air temperature conditions.

It is well known in the art of air heating to use conventional oil burner heater arrangements which include a heating cabinet with an oil burner disposed therein. A motor driven blower is provided to create a draft of air through the cabinet to be heated and to supply air under pressure to the burner for combustion purposes. The burner is connected to the fuel supply by a valve which can be opened to provide fuel to the burner for ignition when the motor driven blower is operating.

Such heater arrangements of the past have been designed to operate at some specific preselected ambient air temperature level to obtain optimum heating eifects, the preselected level usually being somewhere between 60 F. and 70 F. However, when such heater arrangements have been required to operate under conditions where the ambient air temperature has been much lower than the preselected level, for instance below zero, a number of difficulties have arisen. For one thing, at such lower temperatures, burner coking within the burner apparatus itself has resulted, this burner coking leading to problems of flame smothering within the burner pot, afterburning, maintenance and a general lowering of burner output and over-all burner efliciency. With such lowering of burner efficiency, there has resulted a lowering of the outlet temperature of the air to be heated, frequently to a point which has fallen well below the minimum desired level of operation.

The present invention avoids the abovementioned disadvantages and problems of past heaters, providing an apparatus for heating air which eliminated undesirable burner coking and the difficulties associated therewith.

In accordance with the present invention, it is recognized that as the ambient air temperature decreases toward a lower point, such as 30 below zero, the weight of air per unit volume (or density) increases substantially. Accordingly, in past heater arrangements having conventional constant velocity blowers, an increased weight of air per unit volume has resulted in an increased poundage of air per minute that has been delivered as both primary and secondary air to the burner and as ventilating air to be heated. When the poundage of the primary air, or in other words, that air used to convert fuel into combustible gases, has been too great, excessive temperatures of hydrocarbon vapors have resulted and this, in turn, has resulted in the formation of solid carbons in the burner-i.e., the burner coking as referred to above. Furthermore, when the poundage of secondary air to the burner has increased, there has resulted a reduction of the CO percentages in the combustion gases from the burner and this, in turn, has decreased the heating efficiency of the unit. Finally, when there has been an increased air poundage of ventilating air, this has decreased the air outlet temperature of the heater arrangement since a greater weight of air has had to be heated with the same, if not a lesser, number of B.t.u.s available from the burner.

The present invention, recognizing that this increased air poundage produces the above diflicu-lties, provides a Mildi? Fatented Jan. as, was

straighforward and eflicient apparatus for controlling the air poundage as the temperature of the ambient air is lowered without creating internal pressure on the burner pot or increasing the back pressure on the air blower.

Various other features of the invention will become obvious to one skilled in the art upon reading the description set forth herein.

More particularly, the present invention further provides an air heater apparatus including a heating cabinet having a burner containing combustion chamber disposed in the cabinet, an air control system for the heating cabinet comprising air inlet and air outlet means for the cabinet, blower means for supplying air to the cabinet to be heated and air for combustion purposes, damper means cooperable with the air inlet means to control the flow of air therethrough and ambient air temperature responsive damper control means connected to the damper means to regulate the damper means in direct proportion to the absolute temperature of the ambient air supplied to the cabinet to maintain a substantially constant air poundage rate delivered to the heating cabinet.

It is to be understood that various changes can be made in the arrangement, form, and construction of the several parts of the apparatus disclosed herein, Without departing from the scope or spirit of this invention.

Referring to the drawings:

FIGURE 1 is a schematic vertical section of one advantageous embodiment of an air heater according to the present invention;

FIGURE 2 is an enlarged schematic isometric view of the damper and damper control means positioned at the air inlet of the heater of FIGURE 1.

As can be seen in FIGURE 1 of the drawings, the air heater of the present invention is similar in many respects to the air heater disclosed in the inventors copending application, Serial No. 684,100, filed September 16, 1957. The heater comprises a cabinet ll having a circular air inlet 2 positioned at the upper portion thereof and a warmed air outlet 3 positioned at the lower portion. Fastened to the upper portion of the cabinet above the air inlet 2 is a weather baffle 4 and hood arrangement 5. A blower 6 for forcing air through the cabinet 1 is positioned adjacent the air inlet 2 of the cabinet, blower 6 being driven at a substantially constant velocity by an electrical motor 7.

Positioned within cabinet 1 is a combustion chamber 3, the spaced walls of the combustion chamber forming a heat exchange zone 9 therebetween. The combustion chamber 8 is provided in its upper portion with an air inlet opening 11 for admission of air for combustion purposes and an exhaust stack outlet means 12 which can be connected to a chimney (not shown) to carry the exhaust gases away. A baflle 13 is also provided in the upper portion of the combustion chamber to insure uniform distribution of the exiting exhaust gases and to prevent such gases from short circuiting directly to the exhaust stack outlet means. Forming the lower portion of combustion chamber 8 is burner casing 14, the burner casing having supported therein perforated burner pot 16. The floor of burner pot 116 is provided with an opening 17 connected to inlet opening 11 of the combustion chamber by preheat tube 18, a cone shaped fiame-spreaded 19 being carried on the tube 18 above the burner pot. A hand port 21 is provided in cabinet 1 including an access tube (not shown in detail), projecting through chamber 8 and spanning the heated air stream to permit the insertion of a hand torch for ignition of the heater.

Connecting burner pot to to a fuel supply tank 22 is a fuel line 23. Included in this fuel line successively from the tank to the burner pot is a float valve mechanism 24 which maintains a constant pressure head for 3 flow control, a metering orifice 26, a manual control valve 27 and a solenoid actuated shut-off valve 28. The opening or closing of shut-off valve 28 is dependent upon the operation of its solenoid, which solenoid can be included in a circuit that advantageously permits the blower to first be operated before the solenoid causes valve 28 to open to admit oil to the burner for ignition. Since such a circuit has been previously disclosed, specific details are not set forth herein. In this connection, it is to be understood that anyone of a number of circuits which include this feature, as well as other desirable features, can be used with the disclosed structure and, if so desired, the air heater control and circuit arrangement set forth in the abovementioned co-pending application, Serial No. 684,100, can be incorporated with the disclosed heater arrangement.

Referring to FIGURE 2 of the drawings, it can be seen that the weather bafiie 4 has a damper 29 positioned in the air path to air inlet 2 before the blower 6. Damper 29 is constructed to include an arm 31 at one end thereof which arm passes through slot 32 in guide bracket 33 mounted on top of cabinet 1. The other end of damper 29 is cut away, as at 34, in such a manner that the cut away portion is of a radius substantially similar to the radius of circular air inlet 2. Accordingly, as damper 29 is moved over inlet 2, the inlet area is decreased gradually in arcuate increments to permit accurate air flow control through such inlet.

To cause damper 29 to move over inlet 2, arm 31 of the damper is connected to one extremity of a bimetallic element 36. Bi-metallic element 36 is positioned within weather battle 4 so as to be in the path of ambient air drawn into the heating cabinet through the circular air inlet 2 by the motor driven blower 6. The bi-metallic element can be any one of a number of conventional type elements made from two dissimilar metals and which is sensitive to temperature changes. In one example of the invention, the bi-metallic element can be selected to regulate the volume of air moved per minute by blower 7 over a range of ambient air temperatures from plus 70 F. to minus 30 F. in such a manner that the poundage of air per minutes delivered to the heater cabinet for combustion purposes and to be heated remains substantially constant. Thus, with one straight forward control arrangement, the past problems of burner coking and the disadvantages arising therefrom are avoided and efficient, clean and economical heating is obtained.

The invention claimed is:

1. In air heater apparatus including a heating cabinet and an inner heating unit having a vaporizing type fuel burner and a combustion chamber, said unit being disposed in said cabinet in spaced relationship therewith, an air control system for said heating cabinet comprising air inlet and air outlet means for said cabinet, blower means cooperating with said air inlet means for supplying air therethrough to said cabinet to be heated, means diverting part of the air delivered by said blower means to said combustion chamber for combustion purposes, damper means cooperable with said air inlet means to control the flow of air therethrough and ambient air temperature responsive damper control means connected to said damper means to regulate said damper means in direct proportion to the absolute temperature of the ambient air supplied to said cabinet to maintain a substantially constant air poundage rate delivered to said heating cabinet.

2. In air heater apparatus including a heating cabinet and an inner heating unit having a vaporizing type fuel burner and a combustion chamber, said unit being disposed in spaced relationship therewith, an air control system for said heating cabinet comprising air inlet and outlet means for said cabinet, blower means positioned adjacent said inlet means for moving a stream of ambient air through said inlet means into said cabinet to be heated, means diverting part of the air delivered by said blower means to said combustion chamber for combustion purposes, damper means cooperable with said air inlet means to control the flow of the stream of air therethrough, and ambient air temperature responsive damper control means positioned in the path of said stream of ambient air to regulate said damper in direct proportion to the absolute temperature of said ambient air as it passes through said inlet to maintain a substantially constant air poundage rate delivered to said heating cabinet.

3. In air heater apparatus including a heating cabinet and an inner heating unit having a vaporizing type fuel burner and a combustion chamber, said unit being disposed in said cabinet in spaced relationship therewith, an air control system for said heating cabinet comprising air inlet and outlet means for said cabinet, blower means cooperating with said air inlet means for supplying air therethrough to said cabinet to be heated, means diverting part of the air delivered by said blower means to said combustion chamber for combustion purposes, damper means cooperable with said air inlet means to control the flow of air therethrough, and a bi-metallic ambient air temperature responsive control connected to said damper means to regulate said damper means in direct proportion to the absolute temperature of the ambient air as it passes through said inlet to maintain a substantially constant air poundage rate delivered to said heating cabinet.

4. In air heater apparatus including a heating cabinet and an inner heating unit having a vaporizing type fuel burner and a combustion chamber, said unit being disposed in said cabinet in spaced relationship therewith, an air control system for said heating cabinet comprising air inlet and outlet means for said cabinet, blower means positioned within said cabinet adjacent said air inlet means for supplying air therethrough to said cabinet to be heated, means diverting part of the air delivered by said blower means to said combustion chamber for combustion purposes, damper means positioned in cooperating relationship with said air inlet means on the inlet side of said blower to control the flow of air through said inlet means into said blower, and a bimetallic ambient air temperature responsive control positioned outside said cabinet and connected to said damper means to regulate said damper means in direct proportion to the absolute temperature of the air as it passes through said inlet to maintain a substantially constant air poundage rate delivered to said heating cabinet.

References Cited in the file of this patent UNITED STATES PATENTS 1,583,238 Scudder May 4, 1926 1,655,246 Schermuly Jan. 3, 1928 2,385,096 McCollum Sept. 18, 1945 2,387,583 Hess Oct. 23, 1945 2,393,167 Holthouse Jan. 15, 1946 2,643,107 Kamm et al June 23, 1953 2,758,591 Hubbard Aug. 14, 1956 FOREIGN PATENTS 64,927 France July 27, 1955 

